In the first-choice vote, Boris leads Ken by 43-38% - again similar to last time.

Brian Paddick is a distant third, on 7%, down from 10% last time

44% of voters think Boris has run a ‘good’ or ‘excellent’ campaign, compared with 29% for Ken and 11% for Paddick

However, by a narrow 39-36% margin, Ken is thought to have achieved more as Mayor

Labour enjoys a 10 point lead over the Conservatives in the election to the Assembly – an 8.5% swing since 2008, when the Tories enjoyed a 7 point lead.

Our final projection for the 25-seat Assembly is:

Lab 11 (up 3 from 2008)

Con 8 (down 3)

LD 2 (down 1)

UKIP 2 (up 2)

Green 2 (no change)

BNP 0 (down 1)

Our prediction of two seats each for the Lib Dems, Greens and UKIP shows how close the race is for third place in the list section of the Assembly vote. Our poll places the Lib Dems very narrowly ahead, but the differences are well within the margin of error. I cannot rule out the Lib Dems ending up in FIFTH place

The BNP look certain to lose their seat in London’s Assembly. Four years ago, they just passed the 5% hurdle. Our poll shows them with just 1% support. Even if they do better than their poll rating, as they have sometimes done in the past, I would be surprised if they end up with more than 2-3%.

The difference between the Mayor and Assembly results is striking: a large swing to Labour since 2008 in voting for the Assembly, but no swing in the vote for Mayor.

The main reason is the "Boris Labour" vote. We looked at people who told us they were certain to vote today, and would vote Labour if today’s contest were a general election. One in ten told us they will vote for Boris. If they voted for Ken, he'd win by 52-48%. Another one-in-ten Labour supporters will withhold their mayoral vote from both men (though most will vote Labour in the Assembly election). If they all backed Ken, he'd win by 54-46%.

To explore why Labour London is likely to re-elect a Tory Mayor, we asked Ken and Boris's supporters for their main reason for backing their candidate.

54% of Boris supporters gave a "personality" reason (they like Boris or dislike Ken), while just 27% gave a "party" reason (they generally vote Tory or dislike Labour)

With Ken the figures are broadly reversed. Only 29% gave a personality reason, while 45% gave a party reason.

Most dramatic are the figures for main reason given by Labour supporters who prefer Boris:

‘I dislike Ken’: 65%

‘I like Boris’ 23%

‘My family would be better off with Boris as Mayor’ 2%

Boris is also helped by those normally Tory supporters who are disenchanted with David Cameron and would vote UKIP in a general election. They prefer Boris to Ken by ten-to-one.

However the larger lesson is that Labour chose a candidate who has lost his voter-appeal. In 2000, when he won the mayoralty as an Independent, Ken was hugely more important than Labour. In 2004, when he won a second term but this time as Labour’s candidate, there was also a ‘Ken bonus’ as, once again, he outperformed his party. By 2008, the Ken bonus had largely disappeared. Now, it is Boris who enjoys a massive bonus and Ken who has proved to be a liability.

Technical note: YouGov polled 2,119 London electors online between Monday and Wednesday. Our final voting prediction is based on the 1,238 respondents who told us they were certain to vote. Among all respondents, the result is virtually a dead heat, with Boris a fraction over 50% and Ken a fraction under 50%. But whereas 68% of Boris's supporters say they are certain to vote, the figure for Ken's supporters is only 62%.